<!DOCTYPE html>
<html>
<head>
    <title>Полукруг</title>
    <style>
        .semicircle {
            width: 200px;
            height: 100px;
            background-color: #4CAF50;
            border-radius: 100px 100px 0 0;
        }
    </style>
</head>
<body>
<div class="semicircle"></div>
</body>
</html>